The present process relates to the preparation of electrodes for use in oxidation processes. More particularly, the present invention relates to the preparation of nickel-oxide hydroxide electrodes by the technique of galvanostatic cycling.
Electrochemically generated nickel-oxide hydroxide electrodes are previously known in the art. Previous processes for preparation thereof involve Kandler deposition of nickel hydroxide layer from a nickel salt solution onto a metal support followed by electrochemical conversion to active nickel-oxide hydroxide in, e.g., caustic electrolyte. The process is well-known having been described in G. Vertes et al., J. Electroanal. Chem., 52, 47 (1974); Kaulen et al., Synthesis Comm., 513 (1979); and other references.
Nickel-oxide hydroxide electrodes are very active and selective for numerous oxidation processes. In particular, the electrodes are useful for the conversion of alcohols to ketones or aldehydes and also carboxylic acids, J. Electrochem. Soc., 124, 203 (1977). As a particular example (poly)alkylene glycols may be converted to the corresponding dicarboxylic acids in high selectivity and current efficiency. The dicarboxylic acids are valuable commercial chelating agents and anticorrosion agents.
It would be desirable to provide a process for preparation of a nickel-oxide hydroxide electrode that does not require the use of a nickel salt solution. Previous processes (Kandler process) require two steps, i.e., treatment of an electrode first with nickel salt solution then with caustic solution. In large scale operations the necessary equipment to perform both steps of the process is both expensive and cumbersome and the process employs toxic nickel salts that are environmentally unacceptable. In addition, the nickel-oxide hydroxide prepared by the Kandler deposition has been found to lack sufficient physical stability for acceptable commercial performance.